CP 1st grader who can't speak--different teaching techniques

I have a 1st grade grandson I take care of who has cerebral palsy. The biggest challenge we are experiencing in school is that he is non verbal. It affects his ability to read and also math because you learn by repeating. And since he doesn't talk (except ASL) he doesn't get the phonics part of reading.

Does anyone have any information on different techniques that can be used in teaching a non verbal child? I have searched the web but have come up with nothing. He is a very smart child.